The present invention relates to an electronic musical instrument utilizing a tone generator of a delayed feedback type, and more specifically relates to control technology for efficiently operating the tone generator to full extent of its expressive ability of musical sound. There has been known a conventional tone generator composed of an electronic loop circuitry which simulates a sounding mechanism of an acoustic musical instrument. For example, Japanese Patent Application Laid-open No. 294692/1990 discloses a tone generator simulating a sounding mechanism of a wind instrument. Japanese Patent Application Laid-open No. 161799/1991 discloses another tone generator simulating a sounding mechanism of a stringed instrument. These conventional tone generators are constructed commonly of a delay element and a feedback path for returning a delayed signal to the delay element, and therefore are called "delayed feedback type". The tone generator of the delayed feedback type is utilized not only to simulate various acoustic instruments, but also to synthesize an artificial musical tone which is newly created by the electronic musical instrument based on the principle of delayed feedback loop synthesis. While other conventional tone generators of a waveform memory type or an FM type basically operate to increment an address of a waveform memory by a given speed to read out a desired tone waveform, the above noted tone generator of the delayed feedback type is operated basically by inducing an oscillation in a closed loop formed by the delay element and the feedback path. Therefore, an external input of a certain excitation signal is required for exciting the closed loop. A delicate variation of the excitation signal could impart significant artistic expression to the synthesized musical tone. For example, in the electronic musical instrument disclosed in the first-mentioned prior art reference, an excitation signal is torn-ted according to initial and after touch data inputted by means of a keyboard and additional data inputted by means of a mouse controller. In case of the second-mentioned prior art, an excitation signal is formed based on manipulation information of a joystick.
These of mouse controller and joystick are provided to supplement a keyboard which is difficult to input diverse and delicate performance manner. However, the mouse controller and joystick have rather a mechanical and rigid construction, and therefore are not suitable for inputting expressive and flexible performance manner, thereby failing to derive full ability from the tone generator of the delayed feedback type.